The BCL2 Inhibitor Venetoclax Plus Rituximab Is Active in MYD88 Wild-Type Polyneuropathy With Anti-MAG Antibodies

Neuropathy with anti-myelin-associated glycoprotein antibodies: update on diagnosis, pathophysiology and management

Antimyelin-associated glycoprotein (MAG) neuropathy is a rare autoimmune demyelinating peripheral neuropathy caused by IgM autoantibodies targeting MAG. The typical presentation is that of a slowly progressive, distal, length-dependent, predominantly sensory, sometimes ataxic neuropathy, frequently accompanied by upper limb tremor. Distal motor weakness may subsequently occur. The clinical presentation may vary and rarely be consistent with that of typical chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), as well as have an aggressive and rapidly disabling course. The diagnosis of anti-MAG neuropathy is based on the detection of anti-MAG antibodies through ELISA or western blot analysis, primarily in presence of an IgM monoclonal gammopathy. Anti-MAG neuropathy may occur without or with haematological malignancy. Electrophysiology is characteristic of a predominantly distal demyelinating neuropathy. Intravenous immunoglobulins and plasma exchange have unproven benefits, but may provide short-term effects. Cytotoxic therapies are commonly used, although without an evidence base. Rituximab, an anti-B-cell monoclonal antibody was studied in two randomised controlled trials, neither of which achieved their primary outcome. However, a meta-analysis of these two studies demonstrated improvement of disability at 8-12 months. A recent trial with lenalidomide was interrupted prematurely due to a high rate of venous thromboembolism. There are currently two ongoing trials with Bruton's tyrosine kinase inhibitors. Symptom control is otherwise frequently needed. Outcome measures used for other inflammatory neuropathies present limitations in anti-MAG neuropathy. International registries such as the planned IMAGiNe study may, in future, provide answers to the many remaining questions.

Recent insights into haematology and peripheral nerve disease

PURPOSE OF REVIEW

The association between clonal haematological disorders and peripheral nerve disease is recognized. Paraproteinaemic phenomena are the most common mechanism, but direct neural lymphomatous infiltration is seen and can be challenging to diagnose. Traditional and novel anticancer therapies have neuropathic side effects.

RECENT FINDINGS

Novel studies using sensitive techniques are refining the incidence of peripheral neuropathy in patients with a monoclonal gammopathy, and the pathogenesis of IgM Peripheral neuropathy (PN) and POEMS syndrome. Recent series give insight into the characteristics and diagnostic challenges of patients with neurolymphomatosis and amyloid light chain amyloidosis. There is an increasing repertoire of effective anticancer drugs in haematological oncology, but chemotherapy-related neuropathy remains a common side effect.

SUMMARY

This review of the current literature focuses on recent updates and developments for the paraproteinaemic neuropathies, and the evaluation, diagnosis and treatment of peripheral nerve disease due to high-grade and low-grade lymphomas and lymphoproliferative disorders.

Anti-MAG neuropathy: historical aspects, clinical-pathological correlations, and considerations for future therapeutical trials

BACKGROUND

 Patients with anti-MAG neuropathy present with distal demyelinating polyneuropathy, IgM monoclonal gammopathy, and elevated titers of anti-MAG antibodies.

OBJECTIVE

 This paper reviews what is known about the clinical presentation, course, pathophysiology, and treatment of anti-MAG neuropathy, with considerations for the design of therapeutic trials.

METHODS

 A literature review of the medical and scientific literature related to anti-MAG neuropathy, and the design of therapeutic clinical trials in peripheral neuropathy.

RESULTS

 Anti-MAG neuropathy can remain indolent for many years but then enter a progressive phase. Highly elevated antibody titers are diagnostic, but intermediate titers can also occur in chronic inflammatory demyelinating polyneuropathy (CIDP). The peripheral nerves can become inexcitable, thereby masking the demyelinating abnormalities. There is good evidence that the anti-MAG antibodies cause neuropathy. Reduction of the autoantibody concentration by agents that target B-cells was reported to result in clinical improvement in case series and uncontrolled trials, but not in controlled clinical trials, probably due to inadequate trial design.

CONCLUSION

 We propose that therapeutic trials for anti-MAG neuropathy include patients with the typical presentation, some degree of weakness, highly elevated anti-MAG antibody titers, and at least one nerve exhibiting demyelinating range abnormalities. Treatment with one or a combination of anti-B-cell agents would aim at reducing the autoantibody concentration by at least 60%. A trial duration of 2 years may be required to show efficacy. The neuropathy impairment score of the lower extremities (NIS-LL) plus the Lower Limb Function (LLF) score would be a suitable primary outcome measure.

Time course of the autoantibody response to therapy in anti-MAG neuropathy: TWO case REPORTS

Background

Anti-MAG neuropathy is a slowly progressive demyelinating neuropathy that can lead to disability. The neuropathy is thought to be caused by monoclonal IgM antibodies that target the Myelin Associated Glycoprotein (MAG) in peripheral nerves. Therapy is directed at lowering the autoantibody concentrations with B-cells depleting agents, most often rituximab, based on case series and uncontrolled trials reporting improvement. There are no FDA approved treatments for anti-MAG neuropathy, however, and two relatively short duration randomized controlled trials with rituximab failed to achieve their pre-specified primary endpoints. There is also little information regarding the number or duration of treatments that are required to effectively reduce the antibody concentrations.

Case presentations

We report the time course of the anti-MAG antibody response in two patients with anti-MAG neuropathy that were treated with rituximab for several years. A reduction of 50% in the anti-MAG IgM was seen after 19 and 58 months respectively, and of 70% after 74 or 104 months of treatment respectively. Titres remained low, without evidence of recurrence after the treatments were discontinued.

Conclusion

Therapy of anti-MAG neuropathy with rituximab may require repeat treatments over more than one year to achieve a significant reduction in autoantibody concentrations. These considerations should inform treatment decisions and the design of clinical trials.

Clinical, biological, electrophysiological and therapeutic profile of patients with anti-MAG neuropathy according to MYD88L265P and CXCR4 mutations and underlying haemopathy

INTRODUCTION

Anti-MAG neuropathies are associated with an IgM monoclonal gammopathy of undetermined significance (MGUS) or with a malignant haemopathy. Our objective was to determine whether the presence of a haemopathy or somatic mutations of MYD88 and CXCR4 genes influences disease presentation and response to rituximab (RTX).

METHODS

We included 79 patients (mean age 74 years, disease duration 9.68 years) who had a bone marrow aspiration with morphologic and immunophenotypic analysis. MYD88L265P and CXCR4 mutations were analysed in peripheral B cells. Information collected included: inflammatory neuropathy cause and treatment sensory sum score (ISS), MRC testing, overall neuropathy limitation scale (ONLS), Rash-built Overall Disability Score (RODS), ataxia score, anti-MAG titres, peak IgM dosage, neurofilament light chain levels, motor and sensory amplitudes, motor unit index (MUNIX) and motor unit size index (MUSIX) sum scores. Efficacy of RTX was evaluated at 12 months in 26 patients.

RESULTS

Malignant haematological disorders were discovered in 17 patients (22%): 13 Waldenstrom macroglobulinemia, 3 marginal zone lymphoma and one mantle cell lymphoma. MYD88L265P mutation was detected in 29/60 (48%) patients and CXCR4 in 1 single patient. Disease severity, biological and electrophysiological data and response to RTX were comparable in patients with MGUS/lymphoma and patients with/without MYD88L265P mutation. ISS was lower and MUSIX higher in patients improved by RTX.

CONCLUSIONS

MYD88L265P mutation and underlying haemopathies are not predictive of a more severe disease. However, in cases of resistant and progressive neuropathy, they provide an opportunity to prescribe newly available drugs such as Bruton tyrosine kinase inhibitors.

FKBP5 activates mitophagy by ablating PPAR-γ to shape a benign remyelination environment

Multiple sclerosis (MS) is an autoimmune and neurodegenerative disease of the central nervous system (CNS) that is characterized by myelin damage, followed by axonal and ultimately neuronal loss, which has been found to be associated with mitophagy. The etiology and pathology of MS remain elusive. However, the role of FK506 binding protein 5 (FKBP5, also called FKBP51), a newly identified gene associated with MS, in the progression of the disease has not been well defined. Here, we observed that the progress of myelin loss and regeneration in Fkbp5ko mice treated with demyelination for the same amount of time was significantly slower than that in wild-type mice, and that mitophagy plays an important regulatory role in this process. To investigate the mechanism, we discovered that the levels of FKBP5 protein were greatly enhanced in the CNS of cuprizone (CPZ) mice and the myelin-denuded environment stimulates significant activation of the PINK1/Parkin-mediated mitophagy, in which the important regulator, PPAR-γ, is critically regulated by FKBP5. This study reveals the role of FKBP5 in regulating a dynamic pathway of natural restorative regulation of mitophagy through PPAR-γ in pathological demyelinating settings, which may provide potential targets for the treatment of demyelinating diseases.

Anti-myelin-associated glycoprotein neuropathy: Where do we stand?

Myelin-associated glycoprotein (MAG) is a transmembrane glycoprotein concentrated in periaxonal Schwann cell and oligodendroglial membranes of myelin sheaths that serves as an antigen for immunoglobulin M (IgM) monoclonal antibodies. Individuals who harbor anti-MAG antibodies classically develop a progressive autoimmune peripheral neuropathy characterized clinically by ataxia, distal sensory loss, and gait instability, and electrophysiologically by distally accentuated conduction velocity slowing. Although off-label immunotherapy is common, there are currently no proven effective disease-modifying therapeutics, and most patients experience slow accumulation of disability over years and decades. The typically slowly progressive nature of this neuropathy presents unique challenges when trying to find effective anti-MAG therapeutic agents. Drug development has also been hampered by the lack of validated outcome measures that can detect clinically meaningful changes in a reasonable amount of time as well as by the lack of disease activity biomarkers. In this invited review, we provide an update on the state of clinicometric outcome measures and disease activity biomarkers in anti-MAG neuropathy. We highlight the insensitivity of widely used existing clinicometric outcome measures such as the Inflammatory Neuropathy Cause and Treatment (INCAT) disability score as well as the INCAT sensory subscore in anti-MAG neuropathy, referencing the two previous negative randomized controlled clinical trials evaluating rituximab. We then discuss newly emerging candidate therapeutic agents, including tyrosine kinase inhibitors and enhanced B-cell-depleting agents, among others. We conclude with a practical approach to the evaluation and management of anti-MAG neuropathy patients.

Real-world evidence on venetoclax in chronic lymphocytic leukemia: The Italian experience

Chronic lymphocytic leukemia (CLL) is the most common form of adult leukemia in the western world. In Italy, venetoclax was approved for use in patients with CLL as monotherapy in 2017 and in combinations in 2019. As a result of this delayed approval, there are relatively few real-world studies from Italian clinical practice and much of the data are in heavily pretreated patients. We have collected the available studies in Italian routine practice. Three studies confirm the effectiveness and tolerability of this agent in patients with relapsed/refractory CLL and high-risk disease characteristics, many of whom had received prior B-cell receptor signaling treatment. Addition of rituximab to venetoclax produced more complete responses in patients with relapsed/refractory CLL, while higher disease burden and progression while receiving a prior Bruton's tyrosine kinase inhibitor were both associated with poorer outcomes in patients treated with venetoclax. Venetoclax was well-tolerated with low discontinuation rates. No studies of venetoclax plus obinutuzumab for the first-line treatment of patients with CLL were available due to the short time since approval in Italy. Several cohorts addressed the impact of COVID-19 on patient management and outcomes, suggesting that treated patients and those in clinical observation had similar rates of COVID-19-related hospital admission, intensive care unit admission, and mortality. Overall, the responses and tolerance to venetoclax observed in the Italian real-world setting confirm the tolerability and effectiveness of venetoclax regimens in high-risk patients.

Mutational Profile in 75 Patients With Anti-Myelin-Associated Glycoprotein Neuropathy: Clinical and Hematologic Therapy Response and Hints on New Therapeutic Targets

BACKGROUND AND OBJECTIVES

Neuropathy with antibodies to myelin-associated glycoprotein (MAG) is the most common paraproteinemic IgM neuropathy. Recently, the mutational profile of the MYD88 and CXCR4 genes has been included in the diagnostic workup of IgM monoclonal gammopathies. The objective of our study was to assess the prevalence of MYD88 L265P and CXCR4 S338X gene variants in patients with anti-MAG antibody neuropathy. Secondary aims were to evaluate possible correlations between the mutational profile and neuropathy severity, antibody titers, and treatment response.

METHODS

Seventy-five patients (47 men, mean age at molecular analysis 70.8 ± 10.2 years; mean disease duration 5.1 ± 4.9 years) with anti-MAG antibody neuropathy were recruited. Among them, 38 (50.7%) had IgM monoclonal gammopathy of undetermined significance, 29 (38.7%) Waldenstrom macroglobulinemia (WM), and 8 (10.6%) chronic lymphocytic leukemia/marginal zone lymphoma/hairy cell leukemia variant. Molecular analysis was performed on DNA from the bone marrow mononuclear cells in 55 of 75 patients and from peripheral mononuclear cells in 18 of 75 patients. Forty-five patients were treated with rituximab, 6 with ibrutinib, 2 with obinutuzumab-chlorambucil, and 3 with venetoclax-based therapy. All the patients were assessed with the Inflammatory Neuropathy Cause and Treatment (INCAT) Disability Scale, INCAT Sensory Sum Score, and MRC Sum Score at baseline and follow-up. We considered as responders, patients who improved by at least 1 point in 2 clinical scales.

RESULTS

Fifty patients (66.7%) carried the MYD88L265P variant, with a higher frequency in WM and naive patients (77.2% vs 33.3%, p = 0.0012). No patients harbored the CXCR4S338X variant. There were no significant differences in hematologic data (IgM levels, M protein, and anti-MAG antibody titers), neuropathy severity, or response to rituximab in MYD88-altered and MYD88 wild-type patients. Nine of 11 (81.8%) patients treated with novel targeted drug, according to the MYD88 status, responded to treatments.

DISCUSSION

MYD88L265P variant has a high prevalence (66.7%) in anti-MAG antibody neuropathy representing a potential effective mutational target for Bruton tyrosine kinase inhibitors. MYD88L265P variant, however, does not seem to be a prognostic factor of neuropathy severity or response to rituximab. In patients not responding or becoming refractory to rituximab, a tailored therapy with new effective target therapies should be considered.

Autocrine TNF-α Increases Penetration of Myelin-Associated Glycoprotein Antibodies Across the Blood-Nerve Barrier in Anti-MAG Neuropathy

BACKGROUND AND OBJECTIVES

Deposition of myelin-associated glycoprotein (MAG) immunoglobulin M (IgM) antibodies in the sural nerve is a key feature in anti-MAG neuropathy. Whether the blood-nerve barrier (BNB) is disrupted in anti-MAG neuropathy remains elusive.We aimed to evaluate the effect of sera from anti-MAG neuropathy at the molecular level using our in vitro human BNB model and observe the change of BNB endothelial cells in the sural nerve of anti-MAG neuropathy.

METHODS

Diluted sera from patients with anti-MAG neuropathy (n = 16), monoclonal gammopathies of undetermined significance (MGUS) neuropathy (n = 7), amyotrophic lateral sclerosis (ALS, n = 10), and healthy controls (HCs, n = 10) incubated with human BNB endothelial cells to identify the key molecule of BNB activation using RNA-seq and a high-content imaging system, and exposed with a BNB coculture model to evaluate small molecule/IgG/IgM/anti-MAG antibody permeability.

RESULTS

RNA-seq and the high-content imaging system showed the significant upregulation of tumor necrosis factor (TNF-α) and nuclear factor-kappa B (NF-κB) in BNB endothelial cells after exposure to sera from patients with anti-MAG neuropathy, whereas the serum TNF-α concentration was not changed among the MAG/MGUS/ALS/HC groups. Sera from patients with anti-MAG neuropathy did not increase 10-kDa dextran or IgG permeability but enhanced IgM and anti-MAG antibody permeability. Sural nerve biopsy specimens from patients with anti-MAG neuropathy showed higher TNF-α expression levels in BNB endothelial cells and preservation of the structural integrity of the tight junctions and the presence of more vesicles in BNB endothelial cells. Neutralization of TNF-α reduces IgM/anti-MAG antibody permeability.

DISCUSSION

Sera from individuals with anti-MAG neuropathy increased transcellular IgM/anti-MAG antibody permeability via autocrine TNF-α secretion and NF-κB signaling in the BNB.

Acute/chronic inflammatory polyradiculoneuropathy

Autoimmune neuropathy may present acutely or with a more progressive and/or relapsing and remitting course. Acute inflammatory neuropathy or Guillain-Barré syndrome (GBS) has variable presentations but by far the most common is acute inflammatory demyelinating polyradiculoneuropathy which is characterized by rapidly progressive proximal and distal symmetric weakness, sensory loss, and depressed reflexes. The most common chronic autoimmune neuropathy is chronic inflammatory demyelinating polyradiculoneuropathy, which in its most typical form is clinically similar to acute inflammatory demyelinating polyradiculoneuropathy (proximal and distal symmetric weakness, sensory loss, and depressed reflexes) but differs in that onset is much more gradual, i.e., over at least 8 weeks. While the majority of GBS cases result from a postinfectious activation of the immune system, presumably in a genetically susceptible host, less is understood regarding the etiopathogenesis of chronic inflammatory demyelinating polyradiculoneuropathy. Both acute and chronic forms of these inflammatory neuropathies are driven by some combination of innate and adaptive immune pathways, with differing contributions depending on the neuropathy subtype. Both disorders are largely clinical diagnoses, but diagnostic tools are available to confirm the diagnosis, prognosticate, detect variant forms, and rule out mimics. Given the autoimmune underpinnings of both disorders, immunosuppressive and immunomodulating treatments are typically given in both diseases; however, they differ in their response to treatment.

Neurological Complications of Conventional and Novel Anticancer Treatments

Various neurological complications, affecting both the central and peripheral nervous system, can frequently be experienced by cancer survivors after exposure to conventional chemotherapy, but also to modern immunotherapy. In this review, we provide an overview of the most well-known adverse events related to chemotherapy, with a focus on chemotherapy induced peripheral neurotoxicity, but we also address some emerging novel clinical entities related to cancer treatment, including chemotherapy-related cognitive impairment and immune-mediated adverse events. Unfortunately, efficacious curative or preventive treatment for all these neurological complications is still lacking. We provide a description of the possible mechanisms involved to drive future drug discovery in this field, both for symptomatic treatment and neuroprotection.

Polyneuropathy Associated with IgM Monoclonal Gammopathy; Advances in Genetics and Treatment, Focusing on Anti-MAG Antibodies

With increasing age, the chances of developing either MGUS or polyneuropathy increase as well. In some cases, there is a causative relationship between the IgM M-protein and polyneuropathy. In approximately half of these cases, IgM targets the myelin-associated glycoprotein (MAG). This results in chronic polyneuropathy with slowly progressive, predominantly sensory neurological deficits and distally demyelinating features in nerve conduction studies. Despite the disease being chronic and developing slowly, it can cause considerable impairment. We reviewed English medical publications between 1980 and May 2022 on IgM gammopathy-associated polyneuropathy, with special attention to studies addressing the pathophysiology or treatment of anti-MAG polyneuropathy. Treatment options have been limited to a temporizing effect of intravenous immunoglobulins in some patients and a more sustained effect of rituximab but in only 30 to 55 percent of patients. An increase in our knowledge concerning genetic mutations, particularly the MYD88L265P mutation, led to the development of novel targeted treatment options such as BTK inhibitors. Similarly, due to the increasing knowledge of the pathophysiology of anti-MAG polyneuropathy, new treatment options are emerging. Since anti-MAG polyneuropathy is a rare disease with diverse symptomatology, large trials with good outcome measures are a challenge.